Wells – Processes – Distinct – separate injection and producing wells
Patent
1994-11-25
1995-11-07
Novosad, Stephen J.
Wells
Processes
Distinct, separate injection and producing wells
166222, 166186, 1663051, E21B 3324, E21B 33138
Patent
active
054640598
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to an apparatus for distributing a current of injection fluid to at least two separate zones having higher and lower injectivity in a ground formation which is penetrated by a well, where the apparatus comprises a pipe element, which by means of upper and lower sealing bodies, defines a space which is adjacent to the zone having the higher injectivity, and which has a connection to the zone, and where a fluid connection is established between the interior of the pipe element and the space via a nozzle which regulates the flow pressure of the current of fluid into the zone having the higher injectivity.
The flow-limiting nozzle is arranged connected to the pipe element in the fluid passage out to the space. Such nozzles are replaceable by means of a tool which is guided down into the well by means of a cable or the like. As fluid water is normally used.
The present invention has to do with the extraction of hydrocarbons (oil/gas) from hydrocarbon-conveying zones in a formation where it is desirable to increase the production by injecting fluid/water into the dissimilar zones via a single well. The reason that special measures are necessary during such injection of fluid into the formation zones, is that such zones have different pressures. The pressure in the zones, and thereby also the resistance to the inflow of fluid to the zones, will consequently vary. The fluid/water will therefore be able to be pumped more easily into the zone which has the lowest pressure, that is to say the higher injectivity, and one risks that little water, if any, reaches forward to the zone with the higher pressure, that is to say the lower injectivity.
This problem is solved by establishing a limitation of the flow of fluid into the zone with the higher injectivity (that is to say an increased pressure drop), in a manner such as is mentioned by way of introduction. The afore-mentioned pipe element has a given length and the nozzle is installed in a side wall pocket which is formed in the pipe element. Normally the space comprises an annular space which is defined by the pipe, the lining and the sealing elements.
In the side wall pocket the nozzle can be mounted and dismounted by means of a tool which is operated from the surface via a cable. The tool which is employed is called a switch over tool. By means of this arrangement a larger proportion of the quantity of fluid flows into the reservoir where the pressure is higher. If the pressure conditions between the formations change, it can be necessary to replace the nozzle with another nozzle which gives a new and more correct pressure drop into the zone which maintains the lowest pressure.
When the well exhibits large deviations from the vertical, it has been found however to be extremely problematic and time-consuming to lift and throw the cable switch over tool with the nozzle into the side wall pocket.
With this background it is an object of the present invention to produce a novel apparatus for injecting fluid into a number of zones of dissimilar injectivity, and where the afore-mentioned drawbacks with positioning the cable-operating tool, are totally eliminated.
The apparatus according to the present invention is characterised in that the pipe element comprises an outer pipe section and arranged internally in relation to the latter an inner pipe section the lower portion of which comprises means for closing off the fluid passage, that a space between the inner and the outer pipe section forms a passage for conveying fluid to the formation zone having the lower injectivity, that the nozzle is arranged in the inner pipe section, and that downstream of the nozzle the inner pipe section is designed with means which form a fluid connection between the inner pipe section and the annular space.
Further specified constructions of the apparatus according to the present invention are evident from the dependent patent claims.
By employing the apparatus according to the invention the result is that the tool which is used to operate the flow-limiting noz
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"Products and Services", Otis Eng. Corp., Sep. 1989, pp. 235-238.
Den Norske Stats Oljeselskap A.S.
Novosad Stephen J.
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